Snap switch



Oct. 3, 1939. J COFFEEN 2,l74,868

SNAP SWITCH Filed Dec. 12. 1936 INVENTOR da /v M COFFEEN A TTORNE YPatented a. a, 1939 UNITED STATES.

PATENT OFFICE 2,114.80: sNsr swn'cn John M. oosesn. New York, N. 1:.

Application Deoember 1:, 1m, Serial No. 115,521;

10 Claims. (cl. zoo-o1 This invention relates to improvements in snapswitches.

More particularly it relates to improvements in snap switches capable ofmaking and breaking 5 either heavy or light electrical circuits veryqulcklyand emciently, and to do this within very close operating limits.

In recent years there has been an extensive development of devicesrequiring pressure switches or switches in which relatively smalldifferences in pressure or travel may be utilized as a circuit closingor opening medium.

It is an object of the present invention to provide a switch, of thesnap type which lends itself to having the contacts in a non-corrosiveand non-oxidizing atmosphere. In accomplishing this object the presentinvention provides astructure enclosing the contacts in a sealed chamberso that dust, dirt, fumes of various kinds, etc.,

cannot adversely reach the contacts, and a structure in which theenclosed chamber may be purged of oxygen, nitrogen and other adverseatmospheric elements, and, if desired, filled with an inert gas such asneon, argon, helium and the .25 like. A complemental object is toprovide such a structure which will be rugged yet small in size.

Another object is the provision of a snap switch which requires butlight pressure or very short travel of an actuator in order to beoperated, and

80 which is highly responsive to slight differences in pressure orslight extents of travel.

A further object of the present invention is to provide a snap switchwhich may be produced economically, and which will be accurate and efasflcient over a long period of time and operation.

In a number of the snap switches of the general type and purpose hereunder consideration which were previously proposed the contacts areaflected by moisture, acid fumes and the like because of their opencondition in industrial locations containing acid, moisture and thelike. When such switches are corroded because of such factors, arcingtakes place and a short life of the switch results.

It is an important object of the present invention to provide a snapswitch in which the contacts will be thoroughly enclosed against acidfumes, moisture and the like, to prevent corrosion and arcing and toinsure a long life to the snap switch.

It is a still further object of the invention to provide a snap switchof small size which may be of one-way or two-way circuit closing form,and in which either or both theone-way and two-way circuit control maybe embodied in the one main out.

,Features of the present invention include the provision of a disheddiaphragm peripherically held in a body, with the diaphragm flexed toone 6 side of a neutral point to normally close or open a circuit whenan actuator is moved by slight. presure or a slight extent, and in whichthe diaphragm serves to enclose contacts in a chambered or cavitysection of the body. Another feature is 10 the provision of a snapswitch structure which may be easily and quickly assembled withoutcritical adjustments, and which may be hermetically sealed if desired. Afurther feature is the provision of a chamber thoroughly enclosing the15 contacts so that there is no danger of arcing contacts igniting gasor the like in atmosphere adjacent the snap switch.

Other objects, features and advantages will be apparent or will appearhereinafter. v 20 In the .drawing, which is merely illustrative of thepresent preferred forms of the invention:

Figure l is a cross-sectional view, taken on line i--l of Figs. 3 and 4.

Fig. 2 is a side view of the snap switch. 25'

Fig. 3 is a sectional view taken on line 33 of Figs. 1 and.2.

Fig. 4 is a plan view of the base member and diaphragm or the lower halfof the snap switch.

8. 5 is a cross-sectional view of a modified form of snap switch.

Pig. 6 is a perspective view of a modified form of actuator.

Fig. discloses the diaphragm in various positions. 35

Before describing the present improvements and mode of operation thereofin detail it should be understood that the invention is not limited tothe details of construction and arrangement of parts shown in theaccompanying drawing, 40

which are merely illustrative of the present preferred embodiments,since the invention is capable of other embodiments, and the phraseology employed is for the purpose of description and not of limitation. 5

Referring now in detail to the drawing, and

to the preferred form of the invention disclosed in Figs. 1 through 4inclusive, the snap switch comprises a body ill, including a base memberll having a cavity I2 and inner shoulder I3, and so a top member I4having a cavity I5. These cupped base and top members II and H arepreferably made of Bakelite or other molded composition and house thevarious operating parts of the snap switch in a novel manner. 55

The base member I I is provided with a bore l6 adapted to receive aterminal l6 molded or forced into place with an integral flange 17against the bottom I8 of the .cavity l2. A terminal screw I9 has athreaded connection 20 with'the terminal I6. A stationary contact 2| maybe made integral with the terminal [6 or, as shown, may be in the formof a separate washer-like plate welded, soldered or otherwise secured tothe terminal I6.

Another stationary contact 23 may be provided, as is shown best in Figs.1 and 3, comprising a U-shaped plate resting upon a shoulder 13 in thecavity l2 with an associated terminal 25 projecting through a bore 26 inthe side wall 2'! of the base member H. A terminal screw 28 isscrew-threaded into the terminal 25. The contact 23 and terminal 25 maybe made integral or, as shown, may be more economically made from twopieces soldered or otherwise secured together. If preferred the outerend of the stationary contact 23 may be secured to the base with a smallscrew 30.

The upper member is provided with an actuator 32, comprising a stud 33extending through a bore 33' in the upper member I4 and having ascrew-threaded connection 34 to a preferably inverted cup-shaped member36 which is locked thereon by a nut 31. Figure 6 discloses a modifledform of actuator 320. like the form just described except that it is ofone piece fibre or Bakelite construction. Intermediate the base member Hand the top member I4 a dished diaphragm 38 is provided which isnormally flexed to one side of a neutral point, as may be apparent byviewing Fig. 1. The diaphragm is peripherically secured to the body IDby the edges 39 and 40 of the members I I and M respectively when thesemembers are secured together as by screws 42, extending through suitablebores 43 and 44, and associated nuts 45 which maintain the diaphragm inits original shape and set over a long period of time even though it isflexed and snapped in regular operation a great many times. The screwsmay be dispensed with and the members merely.cemented together asdescribed hereinafter.

As may be seen best in Figs. 1 and 4 a terminal 46 is secured to theouter edge of the diaphragm as by a slot 41 and solder. A terminal screw48 having a threaded connection 49 serves to conmeet any conventionalcurrent conducting wire to the terminal 46. A stud 50 is secured to thecenter of the diaphragm 38 as by riveting and at its lower end isprovided with a movable contact 5| which, as shown, may also be held onas by riveting.

With that form of. the invention shown in Figs. 1 through 4 control of atwo-way or three-wire electrical circuit may be advantageouslyaccomplished. The diaphragm is normally flexed into the raised positionshown in Fig. 1, whereupon through the stud 50 it carries and maintainsthe movable contact 5| in engagement with the stationary contact 23 tocarry or conduct electrical current from the terminal 46 to the terminal25 or vice versa, the current being transmitted through the diaphragm38, stud 5B and contacts 23 and 5|. However, when a load or travel isimparted to the actuator 32 the inverted cup member 36 presses againstthe dished diaphragm causing it to assume the neutral or almost flatposition. Instantly when the dished diaphragm is moved even aninfinitesimal amount beyond the neutral position and while it is backedby the cup member 36 in this beyond the neutral position it snaps themovable contact 5| into engagement and into operative condition withrespect to the stationary contact. 2|. In this position the circuit isclosed between the terminals 46 and I6.

However, when pressure or travel on the actuator 32 is relievedsuiiiciently to allow the lower edge 58 thereof to move upwardly beyondthe neutral point the diaphragm because of its normal flexed conditionimmediately snaps the associaed movable contact 51 away from thestationary contact 2| (see Fig. '7)

By viewing Fig. 7 it will be noted that when the contacts engage eachother the diaphragm is arrested in a position approximately half asbowed or dished as the normal position thereof, shown in dot-and-dash'lines, and therefore a full snap over which would tend to keep thediaphragm in the down position shown, which would require a. manual pushor pull thereof to effect a return, cannot occur. Thus, with the presentinvention there is always a major force in the diaphragm tending toreturn it to the raised position. 'However, and of particularimportance, when the snap over past the neutral position and toward thelowered position occurs there is a buckling of the diaphragm between thecenter and the periphery thereof toward the actuator, in the nature of aminor force, yieldingly maintaining the contacts in engagement eventhough the actuator is relieved thereon a slight extent. When the loadon the actuator is relieved a predetermined extent the major forceoffsets the minor force and automatically returns the diaphragm to theinoperative position.

Thus, it will be seen that the present invention provides a simple andhighlyefllcient apparatus to control two circuits, for example, to

effect high and low speed operation on an apparatus when a given set ofconditions prevail with respect to the actuator 32. Because the edge 58of thecupped member 36 on the actuator 32 engages the dished diaphragm38 away from the center, near the outer edge thereof, relatively shorttravel of the actuator 32 efiects a considerable travel to the centerand movable contact carrying section oi the diaphragm. Theperiphericallyheld diaphragm is maintained in the normal flexed condition over longperiods, even though it is snapped many times.

This same switch may be used to fully open and close the circuit; forexample, if it is desired to have a circuit normally closed until apredetermined condition occurs current conducting wires are connected tothe terminals 46 and 25 only (not to the terminal l6) whereupon thecircult is closed all the time that the diaphragm 38 is normally flexedinto the position shown in Figure 1. It is normally maintained in thiscondition until a predetermined pressure or travel is imparted to theactuator 32. When the movable contact 5! is snapped away from thestationary contact 23 the circuit between the terminals 46 and 25 isopen.

Similarly if it is desired to have a normal open circuit until apredetermined'condition occurs wires are connected to the terminals 46and I6 (and not to the terminal 25) whereupon the movable contact 5| isaway from the stationary contact l6 providing a normally open circuit.However, when a predetermined pressure or travel is imparted to theactuator 32 the diaphragm 38 snaps the movable contact 5| from theraised position shown in Fig. 1 into engagement with the stationarycontact H to close the circuit between the terminals 46 and I. As soonas a minute degree of lesser pressure or travel is imposed upon theactuator 32, allowing the edge I thereof to return an infinitesimalamount beyond the neutral point, the diaphragm and movable contact 5|snap from the stationary contact 2i, and

circuit closing position, back into the raised and circuit openingposition.

The various views are of enlarged The entire switch may be made so thatit is roughly only approximately an inch square. The diaphragm 3| servesvery efiectively to cover the 'cavity i2 and to change the latter from anormally open cavity to an enclosed chamber protecting the variouscontacts from oxidizing fumes, moisture and other corroding mediumswhich would tend to cause the switch to arc and have a short life. Afterassembly of the snap switch is effected with the screws 42 and nuts 45the assembly may be hermetically sealed by filling a channel Gil with awax 6| or the like. Showing of the various parts in Fig. l is slightlyexaggerated to better illustrate the present invention. In actualpractice only a minute travel need be imparted to the actuator 32 inorder to move the dished diaphragm to either side of the neutral point.

Lugs 62 may be provided on the base member II to accommodate screws IIfor connecting the snap switch at. any desired location.

Fig. 5 discloses a modified form of the present invention which issubstantially the same as the form hereinbefore described in detail.This form of the invention differs from the former form primarily in theprovision of a pivoted movable contact member 64 in the form of a bellcrank having a pivot connection 65 on a terminal block 60. Top andbottom members ii and ll of slightly difierent form are provided merelyto house the difierently shaped movable contact member 84. Also, thestationary contacts are of slightly modifled form including terminals 61and 08 connected to springs 69 and I0. Whenthe diaphragm 38a is in theraised position, as shown in Fig. 5, the movable contact member 04 dropsinto engagement with the contact II to close a circuit between aterminal I! and spring contact ll. However, when the dished diaphragmIla is pressed beyond the neutral point and snapped beyond the lowerpoint by the actuator 32' it throws the movable contact member '4 into araised position into engagement with the spring contact 69 to close thecircuit between the terminals 12 and 61. As with the first form of theinvention the current conducting wires may be connected to any or all ofthe terminals to pro vide a two-way closed circuit, or to provide anopen and closed circuit condition in which the circuit is normally openor normally closed.

In its preferred form, the screws 41 and nuts 45 are dispensed with andthe members of the body thoroughly secured and sealed together as by aBakelite cement or a wax I in the channel 60. Also in this preferredform the sealing ispreferably first effected in the channel 80approximately ninety per cent around the body, excepting only a spacearound the terminal 46 at which point oxygen, nitrogen and other adverseand corroding atmospheric elements are evacuated from the chamberhousing the contacts, and the chamber in turn is filled with anon-corroding or non-oxidizing medium element, such as inert gases suchas neon, argon, helium, either alone or in a combination whereupon thespace around the terminal 46 is sealed with wax or cement ii arelatively short space.

to providea fully enclosed and gas-filled chamber for the contacts.

The form shown in Fig. 5 has the advantage of providing a greater extentof travel to the movable contact so that the snap switch may be used tocontrol and carry heavier electrical loads than is possible with theform shown in Figs. 1 through 4 where the movable contact travelsthrough only Also, it has the advantage of a slight resiliency betweenthe movable contact and the stationary contacts so that the contactsremain together during the slight initial movement of the diaphragmbefore the snap-over occurs. However, the yielding type of contacts may'be also used in that form of the invention shown in Figs. 1 through 4 aswill be readily appreciated by those familiar with the art to which thisinvention appertains.

Other variations and modifications may be made within the scope of thisinvention and portions of the improvements may be used without others.

Having thus described the invention what is claimed as new is:

1. In a snap switch the combination of a body formed by a pair of cuppedmembers; a diaphragm having a snap action in two directions, normallyflexed to one position at one side of its neutral point and exerting acontinuous reaction to return thereto when moved to a position at theother side of the neutral point; means to peripherically secure saiddiaphragm to the cupped members and the latter together; a pusher memberengaging said diaphragm, capa bio of pushing the diaphragm over theneutral point-when a predetermined pressure is applied thereto; andcontacts electrically clcsed by said diaphragm when it ,is moved to aside of the neutral point.

2. In a snap switch the combination of a body; a terminal; a movablecontact; a diaphragm, having a snap action in two directions, normallyflexed to a position at one side of its neutral point and exerting acontinuous reaction to return thereto when moved to a position at theother side of its neutral point, secured to said body, adapted to carrycurrent from said terminal to said movable contact; a stationarycontact;

. and an actuator adapted to operate said diaphragm and movable contactrelative to said stationary contact.

3. In a snap switch the combination of a base member having a cavity; astationary contact in said cavity; a movable contact in said cavity; adiaphragm, having a snap action in two directions, normally flexed to aposition at one side of its neutral point and exerting a continuousreaction to return thereto when moved to a position at the other side ofits neutral point, adapted to cover said cavity and convert it into acompletely enclosed chamber, to protect the contacts therein; anactuator for operating said diaphragm and movable contact; a top member;and means for securing said diaphragm and top member to the base member.

4. In a snap switch the combination of a base member; a stationarycontact; a movable contact; a dished diaphragm secured to the basemember, having a snap action in two directions, normally flexed to aposition at one side of its neutral point and exerting a continuousreaction to return thereto when moved to a position at the other side ofits neutral point, and an actuator for operating said diaphragm andmovable contact relative to the stationary contact.

5. In a snap switch the combination of a base member; a stationarycontact; a movable contact member; a pivoted support for the movablecontact; a diaphragm peripherically secured to the base member, having asnap action in two directions, normally flexed to a position at one sideof its neutral point and exerting a continuous reaction to returnthereto whenmoved to a position at the other side of its neutral point,and an actuator for operating said diaphragm and movable contact member.

6. In a snap switch the combination oi. a base member having a cavity;at least one stationary contact in said cavity; a movable contact; adished diaphragm, having a snap action in two directions, normallyflexed to a position at one side of its neutral point and exerting acontinuous reaction to return thereto when moved to a position at theother side of its neutral point; means peripherically securing saiddiaphragm to the base member with the movable contact substantially atthe center thereof, said diaphragm covering and converting said cavityinto an enclosed chamber to protect the stationary and movable contacts;and an actuator engaging the diaphragm substantially midway between thecenter and peripherically held sections thereof to convert a relativelyshort movement thereof into a relatively long movement to the center ofthe diaphragm and asscciatedmovable contact.

7. In a snap switch the combination of a base member having a cavity; afixed contact in said cavity and having a terminal extending throughsaid base member; a current conducting dished diaphragm having a snapaction in one direction when a predetermined load is applied thereto andhaving a snap action in the other direction when the load is partiallyreleased a predetermined amonnt, said diaphragm being peripheri-= callysecured to said base member to seal said cavity; a movable contactengageable with said fixed contact in the sealed cavity, movable withand electrically connected to said diaphragm; and an actuating: memberfor controlling the load on and action of diaphragm to thereby move themovable contact relative to the fixed contact.

8-. In a snap switch the combination a base member having a cavitytherein; a fixed contact in said cavity; a dished diaphragm normallyflexed to one position at one side 01' its neutral point, exerting acontinuous reaction to return to said position when moved to a secondposition at the other side of its neutral point and having a snap actionin two directions, said diaphragm being peripherically secured to saidbase; a movable contact engageable with said fixed contact in saidcavity and movable by said diaphragm; and an actuating member engageablewith said diaphragm at points spaced from the center' thereof to controlthe action of the diaphragm to thereby move the movable contact relativeto the fixed contact.

9. In a snap switch the combination of a casing; circuit making andbreaking means; a disc having a snap action into operative andinoperative positions in said casing to control said circuit making andbreaking means; an actuator; and means for normally maintaining saiddisc in one of said positions, for maintaining the disc in the other ofsaid positions only while a predetermined pressure is upon the actuatorand for returning the disc automatically to the first position when lessthan said predetermined pressure is applied thereto.

10. In a snap switch the combination of a body; a movable contact; astationary contact; an actuator; and a diaphragm for moving themovablecontact relative to the stationary contact, having operative andinoperative positions, formed to have a major stored force normallyurging the diaphragm to the inoperative position and to have a minorforce yieldingly maintaining said contacts together when a predeterminedforce is applied to the actuator, and automatically loosing the minorforce and allowing the major force to automatically return the diaphragmand movable contact to the inoperative position when less than thepredetermined force is applied to the actuator JOHN Iii. COEFEEN.

